How Far Can a Germ Fly?
Given the presence of the H1N1 (swine flu) virus, chances are this year’s flu season will be fraught with more worry than usual, including continuing debate on how it is spread. Many people know that the virus travels via contact with germ-laden mucus that has been sneezed or coughed out. However, in speaking with Mark Nicas, PhD, MPH, CIH, adjunct professor of industrial hygiene in the School of Public Health at the University of California, Berkeley, who has made a specialty of studying this particular form of transmission, I was surprised to discover how far those little particles can travel.
SALIVA AND MUCUS SPREAD DISEASE
Dr. Nicas’s research primarily centers on building mathematical models of what he calls "the exposure intensity of contaminants in air," which -- when it comes to microbes including the H1N1 virus as well as other viruses, bacteria, molds, and fungal spores -- means studying things like "droplet spray," a nicely euphemistic term for the particles that get coughed or sneezed into the air.
The basics of this research make sense: Larger particles settle out quickly and in limited space, says Dr. Nicas, typically within three feet of origination. In contrast, the smaller particles disperse throughout the room and can be inhaled deeply into the lungs -- and the viruses in these small airborne particles can survive for hours and are able to travel from room to room. If you aren’t blessed with a particularly robust immune system, this can and does lead to increased likelihood of exposure and infection. In Dr. Nicas’s educated opinion, many public health messages have under-stated the risk of infection via the inhalation route.
"If you’re dealing with a new influenza strain such as swine flu," Dr. Nicas told me, "you have to treat all types of exposure pathways as important. There’s no reason to believe that direct droplet spray exposure [meaning you’re at relatively close contact and a particle hits you in the eye or mouth] and hand contact are the only pathways -- inhalation is another and probably even more powerful one."
WHAT THE DOCTOR DOES
I asked Dr. Nicas what measures he personally takes to protect himself and his family during flu season. He washes his hands frequently and avoids touching his nose, mouth and eyes until he’s had an opportunity to wash his hands first. His knowledge of the power of airborne particles has prompted him to minimize the time he spends in crowded venues during the height of flu season, although he says that urban living makes it impractical to always avoid crowded places. Thus far, he is not wearing a respirator mask -- but, he says, if the novel H1N1 virus or any other infectious agent proves to have a high mortality rate, he would consider taking that step as well.
Note from Lucy: I thought this was a good article about how germs get around...With flu season upon us it is important to make sure you build your immune system so that you can fight off these germs.... If anyone is interested, I have a recipe for a flu tonic that would help fight off the flu and build your immune system...
Mark Nicas, PhD, MPH, CIH, adjunct professor of industrial hygiene, School of Public Health, University of California, Berkeley.